Silver dyestuff bleaching process using quinoxaline catalyst

ABSTRACT

A process for the manufacture of color photographic images according to the dyestuff bleaching process is provided. In this process the dyestuff bleaching is carried out in the presence of a dyestuff bleaching catalyst which is a quinoxaline substituted in the 2- and 3-positions by alkyl or aryl groups and also the benzene nucleus may be further substituted. These quinoxalines possess a good activity and effect an advantageous gradation.

United States Patent Schlunke et al.

[151 3,66,93 51 Apr.1&]1972 154] SILVER DYESTUFF BLEACHING PROCESS USING QUINOXALINE CATALYST [72] Inventors: Hans-Peter Schlunke, Marly-le-Petit; Karl Ronco, Riehen, both of Switzerland [30] Foreign Application Priority Data Mar. 13, 1969 Switzerland ..3820/69 [52] US. Cl ..96/53, 96/20, 96/73, 96/99 [51] Int. Cl ..G03c 7/00 [58] Field of Search ..96/53, 99, 73

[56] References Cited UNITED STATES PATENTS 3,429,705 2/1969 Piller et a1 ..96/53 2,669,517 2/1954 Mueller ..96/53 2,270,118 1/1942 Gaspar ..96/99 3,443,949 5/1969 Oetiker et al. .....96/53 3,443,947 5/1969 Mory et al. ..96/53 3,278,303 10/1966 Meyer et al ..96/53 Primary Examiner--J. Travis Brown Att0rneyl-larry Goldsmith, Joseph G. Kolodny and Mario A. Monaco [5 7] ABSTRACT A process for the manufacture of color photographic images according to the dyestuff bleaching process is provided. In this process the dyestuff bleaching is carried out in the presence of a dyestuff bleaching catalyst which is a quinoxaline substituted in the 2- and 3-positions by alkyl or aryl groups and also the benzene nucleus may be further substituted. These quinoxalines possess a good activity and effect an advantageous gradation.

16 Claims, No Drawings alines of formula E wherein A, and A each denote an alkyl residue with at most 5, preferably 1, carbon atoms or an at most bicyclic aryl residue, preferably a benzene residue, D denotes a residue of formula -CN, -OR, COOR, or

Z11 A N/ 2 E are used, wherein A, and A each denote a methyl of phenyl residue, E has the significance indicated and D denotes a residue offormula OR, COOR, or

, wherein R represents an alkyl residue with at most five carbon atoms and R, and R each represent a hydrogen atom or an alkyl group with at most five carbon atoms.

Preferably, quinoxalines of formula [oHa I A2 and especially of formula are used, wherein A D and E have the indicated significance. Quinoxalines which are very suitable correspond to the formula wherein D, denotes an alkoxy group with one to four carbon atoms and E, a hydrogen or halogen atom, an alkyl or alkoxy group with at most 5 carbon atoms, a nitro, amino or alkylamino group with at most four carbon atoms or an acylamino group, and A, and A, nificance. Amongst these quinoxalines, those of formula Dz N Al N M E1 and above all of formula. (7) D2 wherein D denotes a methoxy or ethoxy group and E, denotes a chlorine atom or a methyl, methoxy, nitro, amino, methylamino or acylamino group, with acyl representing the residue of an alkanecarboxylic acid with one to five carbon atoms or of an optionally further-substituted benzenecarboxylic acid or heterocyclic carboxylic acid, and E,, A, and A, have the indicated significance, are of special interest.

Preferred acyl residues in E are residues of alkanecarboxylic acids, for example residues of acetic, propionic or butyric acid or benzenecarboxylic acid residues, for example benzoic acid, toluic acid, chlorobenzoic acid, bromobenzoic acid, nitrobenzoic acid, salicylic acid, methoxybenzoic acid or aminobenzoic acid residues. Possible residues of heterocyclic carboxylic acids are for example residues of pyridinecarboxylic, furanecarboxylic and thiophenecarboxylic acids.

Amongst the quinoxalines of formula (7), quinoxalines of Q: ICE:

and especially those of formula Ion, on a E;

wherein E denotes a methoxy, methylamino or amino group and D and A, have the indicated significance, again occupy a preferred position.

Other quinoxalines of formula (5), with which favourable results are achieved, correspond to the formula have the indicated sigwherein E,, A, and A, have the indicated significance.

Of these quinoxalines, those of formula and especially those of formula CH3 N wherein A E and E have the indicated significance, are preferred.

Here the use of quinoxalines of formula 1 1 -CH N 3 s wherein E has the indicated significance, has proved particularly advantageous.

Quinoxalines which are monosubstituted in the benzene ring preferably correspond to the formula wherein D represents a residue of formula CN, COOR,

, wherein R and R each denote an alkyl residue with at most five carbon atoms or a hydrogen atom, and A and A have the indicated significance.

Here, quinoxalines offormula -At 1), L

are above all very suitable, wherein D, represents a residue of formula COOR,, wherein R denotes an alkyl residue with at most five carbon atoms or a hydrogen atom, and A and A have the indicated significance.

Amongst the quinoxalines of formula 15), those of formula N CHa are of great interest.

lnstead of the free carboxylic acids, it is also possible to employ the corresponding salts, such as for example alkali, ammonium, or alkaline earth salts or other derivatives which can easily be converted into free carboxylic acid under the dyestuff bleaching conditions.

The residues D or D and E in formulae (1) to (4), or the residues D,, D E E and E in formulae (5) to 13), can be in the 5-, 6-, 7- or 8-position of the quinoxaline ring system. Preferably, however, the E and D residues are in the o-position or p-position to one another.

The quinoxalines of fonnula (1) can be used as dyestuff bleaching catalysts in a processing bath, preferably the dyestuff bleaching bath, and/or in a layer of the photographic material.

They can be employed either alone or in the presence of other customary dyestuff bleaching catalysts. It is also possible to employ different quinoxalines of formula (1) simultaneously in the dyestuff bleaching bath. Finally, the qunioxalines of formula (1) can also be employed together with other measures which promote bleaching, such as for example together with an irradiation of the dyestuff bleaching bath or bubbling a gas through the dyestuff bleaching bath or adding organic solvents to the dyestuff bleaching bath.

The quinoxalines of formula (1) can thus be incorporated into a layer which is free of dyestuff which can be bleached image-wise. The multi-layer material can thus for example possess an additional gelatine layer containing only the catalyst, this layer being located directly on the layer support or between two colour layers. In the latter case the layer containing the catalyst also acts as a dividing layer. Furthermore, the catalyst can also be incorporated into colloidal silver or into filter layers containing an organic yellow filter dyestuff or into coating layers. These filter layers, like the layers with the image dyestuffs, appropriately contain gelatine as the layer colloid.

The quinoxalines of formula (1) can however also be directly incorporated into a layer containing an image dyestuff. In other respects, the multi-layer material can display the usual composition. Using the photographic materials of the composition indicated, dyestuff-photographic images can be produced in the usual manner which is in itself known.

The dyestuff bleaching catalysts of formula (1) can however, as already mentioned, also for example be added to the colour bleaching bath, where they then exert their action directly. They can also be added to a prior treatment bath, for example to the developer, a hardening bath, a stopping bath or a special bath before the silver dyestuff bleaching bath. Here a certain part of the amount of catalyst employed is taken up by the photographic layer material and retained until it can then become effective in the dyestuff bleaching bath. The amount of catalyst to be used can vary within wide limits depending on the type of use. In general, it suffices for a strong effect to add 0.001 to 0.l g of catalyst per l litre of a dyestuff bleaching bath of the usual composition which contains a silver complex-forming agent such as for example an alkali bromide or iodide or thiourea and optionally an oxidation protection agent such as for example sodium hypophosphite, and a strong organic or inorganic acid, such as for example benzenesulphonic acid, hydrochloric acid, sulphuric acid, phosphoric acid or sodium bisulphate for reaching the requisite pH-value.

Further subjects of the invention are, accordingly, also a photographic light-sensitive material for the silver dyestuff bleaching process which contains a quinoxaline of formula l as a dyestuff bleaching catalyst in at least one layer on a support, and photographic processing baths, especially dyestuff bleaching baths, characterised in that they contain at least one quinoxaline of formula l as a dyestuff bleaching catalyst.

A further subject of the invention is then a process for the manufacture of color-photographic images according to the silver dyestuff bleaching process on materials which on a support contain at least one silver halide emulsion layer with a dye-stuff which can be bleached image-wise, by exposure, development of the silver image and dyestuff bleaching, characterised in that the dyestuff bleaching is carried out in the presence of at least one quinoxaline of formula l as the colour bleaching catalyst.

The hitherto known compounds used as dyestuff bleaching catalysts in the silver colour bleaching process exert very different effects on azo dyestuffs of different constitution. Whilst they are very effective with one class of azo dyestuffs, they can display only a slight bleaching-promoting effect towards another class. There is thus a need for compounds which by themselves or in combination with others effect a uniformly progressing bleaching of all three layer dyestuffs of a multilayer material.

It has now been found that quinoxalines of formula (I) are outstandingly suitable for this purpose. They are distinguished by an advantageous position of their redox potentials and by good solubility in the requisite concentrations in the dyestuff bleaching bath. The quinoxalines of formula (1) used according to the invention especially possess a good activity and effect an advantageous gradation if the residues A, and A in formula (1) each represent a'methyl group; furthermore the bleaching couplings between the individual layers containing the image dyestuffs are largely suppressed when these quinoxalines are present, and given appropriate use.

The quinoxalines of formula (1 are appropriately manufactured in a manner which is in itself known (compare, in this context, J.C.E. Simpson, Condensed Pyridazine and Pyrazine Rings, in A. Weissberger, The Chemistry of Heterocyclic Compounds, J. Wiley and Sons, New York 1953, 203 et seq.) by condensation of an aromatic l,2-diamine with a l,2-dicarbonyl compound. In place of the diamine, it is also possible to employ the corresponding, significantly more stable, 0-

nitraniline or the corresponding o-dinitro compound, which can be reduced to the desired diamine and then reacted without intermediate isolation to give the quinoxaline. Appropriately substituted benzfuroxanes or their reduction products (benzfurazanes) can also be reduced via intermediate stages to l,2-diamines (F.B. Mallory and SP. Varimbi, J. Org. Chem. 28, 1656 et seq. 1963) and the diamines accessible in this way can be condensed to quinoxalines:

In place of the l,2-dicarbonyl compound it is also possible to react the analogous a-halogenoketone with the o-diamine to give the corresponding l,2-dihydroquinoxaline (J. Figueras, J. Org. Chem. 31, 803 et seq. (1966)), and this is then oxidised in situ to the quinoxaline.

The quinoxalines are obtained in better yield and higher purity if the condensation is carried out under nitrogen. a-Oximinoketones can also be reacted with l,2-diamines to give quinoxalines (compare, in this context, .I.C.E. Simpson, loc. cit.).

In the case of the higher-alkylated alkoxy-quinoxalines it is advantageous to start from the corresponding hydroxy compounds, such as for example 6-hydroxy-2,3-dimethylquinoxaline, which by itself already shows a bleaching-promoting effect in the silver dyestuff bleaching process, these then being reacted in a known manner (A.K. Sen and S. Sarrna, J. Ind. Chem. Soc. 44, 644 (1967)) with an alkylating agent, such as for example n-butyl bromide, in dimethylformamide in the presence of a base such as for example K CO Quinoxalinecarboxylic acid esters and amides can be manufactured by means of methods which are in themselves known, via the corresponding acid chloride or the mixed anhydride. In the latter case, the mixed anhydride of the quinoxaline-carboxylic acid and a chlorocarbonic acid ester is advantageously employed. The simple esters can also be manufactured by direct esterifrcation.

The nitroalkoxyquinoxalines and the aminoalkoxyquinoxalines are accessible by usual nitration and, where appropriate, reduction of the nitro group. If required, the amino group can be acylated according to known methods.

Possible starting materials for one of the syntheses mentioned are for example the compounds listed in the table which follows.

N\\ Ar D N A2 l,2-Dicarbonyl compounds, a-halogenoketones and a-oximino-ketones Diacetyl, 3-bromobutanone-2, 3-oximinobutanone-2, hexane-dione-3,4, benzil, l-phenylpropanediode-l,2, l-phenyl-2- oximinopropanonel bromopropiophenone, di-(a-naphthyD- diketone and di-(B-naphthyD-diketone. o-Nitroanilines or o-dinitrobenzenes, and l,2-diamines 3 ,6-Dimethoxyl ,2-dinitrobenzene, 4-methyl-2-nitraniline, 4-methoxy-2-nitraniline, 4-ethoxy-2-nitraniline, 3-ethoxy-2- nitraniline, 2,3-dinitroanisole, 4,5-dinitroveratrole, 4-amino- 3-nitrobenzoic acid, 3-amino-2-nitrobenzoic acid, 2,3- dinitraniline, 3,6-dimethoxy-2-nitraniline, 3,6-dimethoxy-ophenylenediamine, 4-amino-5-nitroveratrole, 4,5- diaminovera-trole, 4methyl-o-phenylenediamine, 4-methoxyo-phenylenedi-amine, 4-ethoxy-o-phenylenediamine, 2- amino-3-nitroanisole, 2-nitro-3-aminoanisole, 3-methyl-4- amino-S-nitroanisole, 3-methyl-4,S-diaminoanisole, 2,3- diaminoanisole, 4cyano-2-nitraniline, 4-cyano-o-phenylenediamine, 3-cyano-2-nitraniline, 3-cyano-o-phenylenediamine, 2,3-dinitro-4-methylanisole, 2-amino-3-nitro-4- methylanisole, 3-amino-2-nitro-4-methylanisole, 2,3-diamino- 4-methylanisole, 2,3-dinitro-4-methoxy-acetanilide, 2-amino- 3-nitro-4-methoxy-acetanilide, 3-amino-2-nitro-4- methoxyacetanilide, 2,3-diamino-4-methoxy-acetanilide, 2-methoxy- 4,5-dinitroacetanilide, 2-methoxy-4-amino-5-nitro-acetanilide, 2-methoxy-4-nitro-5-aminoacetanilide, 2-methoxy-4,5- diaminoacetanilide, 2-methoxy-4,5-dinitralinine, 2-methoxy- 5-nitro-p-phenylenediamine, 2-methoxy-4-nitro-m-phenylenediamine, 2-methoxy-l,4,5-triaminobenzene, 2,3-dinitro- 4-methoxy-N-methylacetanilide, 2-amin0-3-nitro-4-methoxy- N-methylacet-anilide, 3-amino-2-nitro-4-methoxy-N- methylacetanilide, 2,3-diamino-4-methoxy-N-methylacetanilide, 2,3-dinitro-4-methoxy-N-methylaniline, 3-nitro-4- methoxy-N -methyl-o-phenylenediamine, 2-nitro-4-methoxy- N -methyl-m-phenylenediamine and 4-methoxy-N,-methyll ,2,3-triaminobenzene. Benzfuroxanes 4(7)-chloro-5(6)-methoxybenzfuroxane, 4(7)-chlor-5(6)- ethoxybenzfuroxane, 5(6)-chloro-4(7 )-methoxybenzfuroxane and 5( 6 )-chlor-4( 7 )-ethoxybenzfuroxane. Benzfurazanes 4-Chloro-5-methoxybenzfurazane, 4-chlor-5-ethoxybenzfurazane, 4-methoxy-5-chlorobenzfurazane and 4-ethoxy-5- chloro-benzfurazane. Hydroxy-quinoxalines 6-I-Iydroxy-2,3-diphenylquinoxaline and 6-hydroxy-2,3-dimethylquinoxaline. Mixed anhydrides 6-(Carboxy-carbethoxy)-2,3-diphenylquinoxaline and 6- (carboxy-carbethoxy)-2,3-dimethylquinoxaline. Quinoxalines (for example for nitration) 6-methoxy-2,3-diphenylquinoxaline, 6 methoxy-2,3- dimethyl-quinoxaline, 6-ethoxy-2,3-diphenylquinoxaline and 6-ethoxy-2,3-dimethylquinoxaline.

MANUFACTURING INSTRUCTIONS General Instruction 1 A substituted o-nitraniline derivative is dissolved, or merely suspended, in a suitable solvent, such as for example methanol, ethanol, glacial acetic acid or dimethylformamide, mixed with l to 10 per cent by weight of hydrogenation catalyst such as for example a 10% strength palladium-charcoal catalyst, and hydrogenated under normal pressure, optionally with initial warming. After completion of the reaction, the catalyst is filtered off under N and the filtrate is mixed, under N, with at least the equimolecular amount of distilled or recrystallized diketone or a solution of the diketone in a suitable solvent, whereupon, in most cases, an intensification of colour occurs and the temperature rises. Thereafter the mixture is boiled under reflux until the reaction is complete and the desired substance is isolated after cooling. The product can be purified by recrystallisation from a suitable solvent or, if necessary, by chromatography or sublimation.

Instead of the o-nitraniline derivative, the corresponding 0- dinitro compound is employed in some cases.

1f the appropriate o-phenylenediamine is accessible simply and in adequate purity, it is condensed directly, or in the form of its hydrochloride, with the desired diketone in a suitable solvent under nitrogen. When using the hydrochloride it is advisable to add a corresponding amount of sodium or potassium acetate to neutralise the RC1 liberated.

In order to synthesise 2,3-asymmetric compounds, the adiketone is replaced by a-bromopropiophenone. The 1,2-dihydroquinoxaline thus formed is then oxidised with the Na salt of m-nitrobenzenesulphonic acid in the presence of aqueous NaOl-l to give the quinoxaline.

The redox potentials are determined by means of polarography in the customary manner which is in itself known. A mixture of dimethylformamide-2 N sulphuric acid in the ratio of 1 1 serves as the solvent in all cases. The potential is measured against an Ag/AgCl electrode of known potential and is then recalculated to the potential against a normal hydrogen electrode. Whilst in some cases two single-electron transitions, characterised in that two polarographic waves occur, are observed, only a single polarographic wave is observed in other cases, and this then corresponds to the mean redox potential.

The melting points and analytical results of all qinoxalines of formula (1) which were manufactured are summarized in Table l. A. 6-Ethoxy-2,3-dimethylquinoxaline nitraniline ml 10% 3.55 13.71 100% ml 9.1 g (50 mmols) of 4-ethoxy-2-niraniline are dissolved in 200 ml. of ethanol, mixed with l g of 10 percent strength palladium-charcoal catalyst and hydrogenated at room temperature under normal pressure. The reaction temperature rises to 41 C over the course of 10 minutes and to 53 C over the course of the following 15 minutes, with 3.55 1 of hydrogen being consumed. The temperature then gradually drops to 26 C. The total hydrogen consumption amounts to 3.7 l 100 percent of theory. The catalyst is filtered off in a closed apparatus under nitrogen and the dark red filtrate is mixed with 4.3 g (50 mmols) ofdiacetyl in a stream of nitrogen. The reaction mixture is then heated for 10 minutes under nitrogen to the reflux temperature. After cooling, 300 ml of water are added and the whole is cooled to C. The 6-ethoxy-2,3- dimethylquinoxaline which has precipitated is filtered off, washed with a little water and dried at 60 C in vacuo. Yield 7.1 g (70% oftheory) oflight yellow crystals ofthe compound A. The thin layer chromatogram with chloroform: ethyl acetate 7:3 as the migrating agent shows a single substance with an Rf-value of 0.57. The infrared spectrum and the nuclear resonance spectrum are in agreement with the expected structure. B. 2-Methyl-3-phenyl-6,7-dimethoxyquinoxaline 2.3 g (10 mmols) of 4,5-dinitroveratrole are dissolved in 170 m1 of absolute alcohol, mixed with 0.2 g of 10% strength palladium charcoal and hydrogenated under normal pressure at room temperature. The temperature rises to 38 C over the course of minutes and then again drops to 27 C over the course of a further hour, with 1.47 l 100% of theory) of hydrogen being taken up. The catalyst is filtered off under nitrogen in a closed vessel, with the colourless filtrate being directly charged onto 0.98 g (12 mmols) of sodium acetate. After adding 2.13 g (10 mmols) of freshly distilled bromopropiophenone, the reaction mixture is heated for 3 hours under reflux, whereupon the solution assumes a dark color. A solution of 2.61 g (11 mmols) of sodium m-nitrobenzenesulphonate and 4.4 g 1 l0 mmols) of sodium hydroxide in a mixture of ml of water and 8 ml of ethanol is then added and the mixture heated for a further 2 hours under reflux. The reaction mixture is cooled to room temperature and extracted with 5 portions of 100 ml of ether. The organic phases are washed with 3 portions of 50 ml of 2 N sodium hydroxide solution and 5 portions of 100 ml of water, combined and dried over anhydrous sodium sulphate. After filtering, and evaporating the filtrate, 1.4 g of crude product remain and this is purified by twice recrystallising from ethanol. Yield 0.7 g of theory) of compound B. The thin layer chromatogram in trichloromethane shows two minute traces of impurities alongside a main product. The infrared spectrum and the nuclear resonance spectrum are in agreement with the envisaged structure. C. 5-Methoxy-6-chloro-2,3-dimethylquinoxaline 2 g (10 mmols) of 4(7)-methoxy-5(6)-chlorobenzfuroxane are dissolved in 50 ml of ethyl acetate, mixed with 20 mg of platinum oxide and hydrogenated at room temperature under normal pressure. Over the course of 30 minutes, 900 ml of hydrogen are taken up, with the temperature rising to 49 C. After a further minutes the temperature drops back to 25 C; the entire hydrogen uptake is 970 ml (99.5% of theory). The mixture is diluted with 20 ml of acetic acid ethyl ester, warmed to 40 C and filtered in a closed apparatus under nitrogen. The filtrate is mixed with 1.72 g (20 mmols) of diacetyl and heated for 45 minutes under reflux. After cooling to room temperature, the mixture is evaporated to dryness and the residue (2.1 g) is recrystallised from water/methanol 1 1. Yield 1.4 g; melting point: 835 to 85 C. Sublimation at 80 C and 0.04 mm Hg finally yields 1.3 g (59% of theory) of almost colourless crystals of the compound C.

The thin layer chromatogram with trichloromethane as the migrating agent shows a main zone and a slight impurity. The

infrared spectrum and the nuclear resonance spectrum are in agreement with the expected structure. D. 6-Butoxy-2,3-dimethylquinoxaline 1.6 g (9.2 mmols) of 6-hydroxy-2,3-dimethylquinoxaline, manufactured by ether scission of the 6-methoxy compound, are dissolved in 15 ml of anhydrous dimethylformamide and mixed with 2.54 g (18.4 mmols) of potassium carbonate. After adding 1.47 g (10.8 mmols) of n-butyl bromide, the whole is kept for 30 minutes at C internal temperature whilst stirring and excluding moisture. After slow cooling to 0 C, the colorless crystals which have precipitated are filtered off and washed with a little water and then with a little ice-cold ethanol. Yield: 1.9 g of crude product which is purified by taking up in 5 mlwof dimethylformamide and precipitating with 100 ml of water, so that] .8 g (81% of theory) of compound D are obtained.

It is possible to show by two-dimentional thin layer chromatography with cyclohexane-acetic acid ethyl ester, 6:4, that the compound suffers a certain decomposition at least in solution. The infrared spectrum and the nuclear resonance spectrum are in agreement with the envisaged structure.

E. 5-Nitro-6-methoxy-2,3-dimethylquinoxaline 18.55 g (100 mmols) of 6-methoxy-2,3-dimethylquinoxaline are introduced with stirring into 80 ml of 96% strength sulphuric acid, in the course of which the temperature rises to 70 C. After the solution has been cooled to 0 C, 15.7 g mmols) of 50% strength nitric acid (mixed acid) are added dropwise over the course of 15 minutes in such a way that the internal temperature does not exceed 5 C. Thereafter the mixture is stirred for 4 hours at 0 5 C and is then poured onto 400 g of ice. The crude product which has precipitated is filtered off and suspended in excess 5% strength aqueous sodium carbonate. After renewed filtration and washing with water until neutral, 17.6 g of crude product are produced, which are recrystallised from 280 ml of acetone and 350 ml of water. Yield 12.75 g (56% of theory) of compound E.

The thin layer chromatogram in toluene/acetone, 9:1, shows a slight trace of impurity alongside a single product. The infrared spectrum shows the characteristic absorptions of the functional groups; the nuclear resonance spectrum is in agreement with the envisaged structure.

F. 5-Nitro-6-ethoxy-2,3-dimethylquinoxaline Starting from 6-ethoxy-2,3-dimethylquinoxaline, compound F is obtained in an analogous manner to that described in Instruction E, in a yield of78 to 95% of theory.

The thin layer chromatogram in toluene/acetone, 9:1, shows slight impurities alongside the main product; the infrared spectrum and the nuclear resonance spectrum are in agreement with the structure.

G. 5-Amino-6-methoxy-2,3-dimethylquinoxaline 10 .l. 2,3-Diphenylquinoxaline 6 t rboxylic acid methyl ester chloride as described in ges to lemon yellow gins to separate out. After slow platelets of the compound I.

pectrum ged structure. ylic acid amide quinoxaline-o-carboxylic methoxyethane. After admine, the mixture is cooled to C. 1.2 g (11 mmols) of chloroformic acid ethyl ester are added dropwise with vigorous stirring in such a way that the Analysis, percent Calculated Found 950 mg (2.75 mmols) of the acid Instruction I are heated for 15 minutes in 15 ml of methanol under reflux, whereupon the colour chan and a yellow precipitate be cooling the product is filtered off, washed with a little icecold methanol and dried in vacuo. The 600 mg of ester thus obtained are recrystallised from 40 ml of methanol. Yield 500 mg (54% of theory) of colourless The infrared spectrum and the nuclear resonance s show the bands to be expected for the envisa K. 2,3-Dimethylquinoxaline-6-carbox 2.02 g (10 mmols) of 2,3-dimethyl acid are dissolved in 200 ml of 1,2-di 3- ding 1.01 g(10 mmols) oftriethyla dimethylquinoxaline in an analogous manner to that described in Instruction G.

internal temperature does not exceed 10 C. The mixture is stirred for a further 3 hours at room temperature. After completion of the reaction, 20 ml of 24% strength ammonia are added and the mixture is warmed to 60 C for 1 hour. After evaporation under reduced pressure and recrystallization from methanol, 1.3 g (65% of theory) of colourless crystals of the compound K are obtained. The thin layer chro- 25 matogram with propanol/24% strength ammonia, 8:2, as the migrating agent shows a single substance. The infrared spectrum and the nuclear resonance spectrum are in agreement with the postulated structure. W L. 5-Benzoylamino-6-methoxy-2,3-dimethylquinoxa1ine 1.0 g (5 mmols) of compound G is dissolved in 15 ml of dimethylformamide and mixed with 1.2 g (12 mmols) of triethylamine. After cooling to 0 C, the solution thus obtained is mixed with 1.7 g (12 mmols) of benzoyl chloride whilst stir- 3 5 ring. Stirring is continued for 2 hours at 0 C and the reaction mixture is then poured out onto 200 g of ice-water mixture. The colorless precipitate which thereupon forms is filtered off and washed with cold water. After recrystallization from methanol, 0.7 g (50% of theory) of the compound L are obtained. V V V The thin layer chromatogram with toluene acetone, 9: l, as the migrating agent shows a main zone. The infrared spectrum and nuclear resonance spectrum are in agreement with the postulated structure. W

The compounds M to RR of Table l are manufactured analogously to the compounds A to L.

TABLE I methoxy-2,3-dimethylquinare mixed with ydrogenated at 65 C. 3.4 1 taken up over the course of yst is 5 pound -ethoxy-2,

Resldues in Formula (1) 11.5 g mmols) of 5-nitr6-6- oxaline, dissolved in 1 .000 ml of ethanol Raney nickel (activity W 5) and h of hydrogen 100% of theory) are 2 /2 hours. After cooling to room temperature, the catal filtered off and the filtrate is concentrated in vacuo, clarified by filtration with animal charcoal, and finally evaporated to dryness. Yield 6.2 g (62% of theory) of compound G.

The thin layer chromatogram ,in toluene/acetone, 9:1, shows a slight impurity alongside the main product. The in- 10 frared spectrum and the nuclear resonance spectrum are in agreement with the structure of the desired compound.

H. 5-Amino-6-ethoxy-2,3-dimethylquinoxaline 5-Amino-6-ethoxy-2,3-dimethylquinoxaline com H) is obtained in 65% yield from 5-nitro-6 The thin layer chromatogram in toluene/acetone, 9:1, shows a single product and the infrared spectrum and nuclear resonance spectrum correspond to the structure.

I. 2,3-Diphenylquinoxaline-6-carboxylic acid amide 3.26 g (10 mmols) of 2,3-diphenylquinoxaline-6-carboxylic acid are suspended in 30 ml-of absolute benzene and mixed with 1 ml of dimethylformamide and 1.78 g (15 mmols) of thionyl chloride. On heating, the reaction mixture discolours at C, with the acid slowly dissolving. After 8 hours the evolution of hydrochloric acid gas has ended. The excess thionyl chloride and about half the solvent are stripped in vacuo from the clear red-brown solution. The crystals which have precipitated are filtered off and washed with a little benzene. The infrared spectrum shows the bands which are characteristic for acid chlorides. After taking up in 50 ml of chloroform, adding 1 g of animal charcoal, filtering hot and evaporating the filtrate, 2.1 g (78% of theory) of yellowishtinged crystals of melting point 168 to 169 C (decomposition) are obtained.

l g (2.9 mmols) of the acid chloride thus obtained is heated for 1 hour under reflux with 20 ml of 24% strength ammonia. The colourless crystals which have precipitated after cooling are filtered off, washed with a little cold water and dried in vacuo. Yield 0.9 g (96% of theory). recrystallisation from acetic acid ethyl ester/methanol, 1:1, finally yields fine colourless needles of the compound I, the infrared spectrum of which is in agreement with the envisaged structure. The thin layer chromatogram in chloroform/butyl acetate, 7:3, shows two slight impurities alongside the main zone.

Compound 11.838282828234717 w mmmflwmm wm w ll 1 1 1 1 1 1111 1 2 39588849533 4747Qfn oom 31777832673n0101lf7t m mi w am

m OOHH H lllmmmc Hum 00 NNNN N 000 0 N Table l-Continued Analysis, percent Residues in Formula (1) Melting Calculated Found point Compound A1 A: D E O o. o H N c H N 7 C1111 46060.11. 5 H 151 .1" 7595 -5I2 7. 90 78.00" 5.45 7. 94

CH1 (100001111 H 100. 5 67.81 5. 13 12.15 57. 85 5.17 12. 23

CH; 6-CN H 205. 9 72. 11 4. 95 22. 94 72. 3e 4. 92 22. 9o

CflHs fi-CN H 181. 4 s2. 05 4. 25 13. 57 82. 02 4. 49 13. 64

CH: 6-C0N(C1H5)2 H 73. 3 70. 01 7. 44 1o. 33 59. 97 7.38 15. 96

C1115 6-CON(CH5)1 H 137. 78.71 6.08 11.02 73. 45 5. 10. 97

CH; ti-OCH; 7-NH2 1 252 55. 01 5. 09 20.68 55. 4s 5. 39 20. 24

CH; 5-OCH3 B-NHCH: 151.1 55. 34 0. 95 19. 34 G6. 43 6. 9s 19.

CH: 5-0011: B-CHQ 124.4 71. 25 5. 98 13.85 71. 50 7. 04 13. 91

06H: 5-0011. 8-011; 190. 7 so. 95 5. 55 8.58 81. 04 5. 50 s. 54

1 Decomposition.

EXAMPLE 1 7. 2 minutes soaking 8. 4 minutes fixing as under 2.)

9 10 minutes soaking.

After drying, the image which has been cleanly bleached colourless is obtained with a distinct stepped gradation of the A solution consisting of 3.3 ml of 6% strength gelatine, 2.0 ml of a 1% ml solution of the hardener 2,4-dichloro-6-phenylamino-l,3,5-triazine-3-sulphonic acid, 0.5 ml of a 2.10 molar solution of compound U in dimethylformamide and 4.2

ml of water is cast on a glass plate of size 13 cm X18 cm. After wedge used as the ongmal' drying, a solution consisting of 3.3 ml of 6% strength gelating, 3.3 ml of a silver bromide emulsion, containing 5.3 g of silver EXAMPLE 2 per 100 g of emulsion, 2.0 ml of the above hardener, 0.3 ml of a 1% strength solution of the blue-green dyestuff of formula lf, instead of compound U, the compound 1 is employed and and 1.1 ml of water is cast on top. After drying of the combined layer thus obtained, a step wedge is copied onto it (50 LUX, 3 sec.). Thereafter the copy is developed in accordance with the following instruction:

1. 6 minutes development in a bath which per liter contains 50 g of anhydrous sodium sulphite, 0.2 g of l-phenyl-3- pyrazolidone, 6 g of hydroquinone, g of anhydrous sodium carbonate, 4 g of potassium bromide and 0.3 g of benztriazole 2. 2 minutes fixing with a solution of 200 g of sodium thiosulphate, 10 g of anhydrous sodium sulphite, 20 g of sodium acetate and 10 ml of glacial acetic acid per liter of water 3. 4 minutes soaking 4. 6 minutes dyestuff bleaching with a solution of 10 g of potassium iodide in l lof l N sulphuric acid 5. 2 minutes soaking 6. 2 minutes bleaching of the residual silver with a bath containing 150 ml of 37% strength hydrochloric acid, 25 g of copper sulphate and 30 g of potassium bromide per liter the procedure described in Example 1 is followed, a clean positive image of the exposed wedge is again obtained. If, instead of compound U, compound KK is employed as an acetone solution and the procedure of Example 1 is followed, a clean positive image of the wedge used as an original is again obtained.

The compound U can with equal success be replaced by the compound L, which is applied as an alcoholic solution.

EXAMPLE 3 A photographic material with three color layers contains, on an opaque white cellulose acetate film, a red-sensitive silver bromide emulsion with the blue-green dyestuff of formula on top of this an empty gelatine separating layer, then a greensensitive silver bromide emulsion with the purple dye-stuff of formula 13 l4 (2. 2) NH2 7 H21? O I OH H035 H035 HO- I H 03 S H 03 S After a further separating layer, there follows a layer with a After drying, a grey wedge with clean whites and distinctly yellow filter dyestuff or with colloidal silver acting as a yellow stepped gradation is obtained.

filter. On top of this there is a silver bromide layer with the yelinstead of the compound U, the compound T or the comlow dyestuff of formula pound JJ can be used with equal success.

( H02? CHa iCO SOJH -N=NNH("J- -o OHNC NN-@3 0 H3O CH3 S 03H H03 g and a covering layer. All layers are hardened with a EXAM E halogenotriazine compound such as 2,4-dichloro-6-phen- I PL 6 1 i .1,3,j. i i .3'. l h i id 25 A solution of the following composition is cast onto a glass This copying material is successively exposed under a step P of cm X cm: of Strength gelatine, wedge in the three spectral regions blue (Wratten filter Kodak ml of a sllver bromlqe emulsion whlch comams g of 2 B 49), green (wratten filter Kodak 16 61) and red silver per 100 g of emulsion, l.0 ml of a 1% strength solution (Wratten filter Kodak 2 X 29), and developed for 7 minutes, of the hardePer descnbed Example 03 m1 of a 1% and fixed, as described in Example 1. Thereafter bleaching is 30 strength sohmo ofihe blue'green dyesmff of formula carried out in a silver dyestulf bleaching bath which per liter and m] ofwater' contains 27 ml of 96% strength sulphuric acid, 10 g of potassi- .After drying a wedge cop'ed the layer thus u m iodide and 10 ml of a -2 molar solution of the tamed, and the plate is then treated according to the following pound DD in ethanol. After a brief soaking, the residual silver instruction} is oxidised as described in Example 1 under a) and the l. 10 minutes development in a bath which per liter conmaterial is soaked and fixed as described above. After tains 20 of anhydrous Sodium sulphite, l g of 4- thorough rinsing and after drying, a grey wedge bleached to Ilfthylammophenpl sulphate 4 g of hydroqumqne 10 g white is obtained, the gradation of which corresponds to the o .anhydrous soduim i 2 g of potass'um original. mide and 3 g of sodium thiocyariate;

2. 2 minutes soaking;

EXAMPLE 4 40 3. 2 minutes oxidising with a solution of 5 g of potassium bichromate and 5 ml of 96% strength sulphuric acid per Instead of the compound DD as in Example 3, the comliter ofsolution; pound Z or another of the quinoxalines quoted in Table I, dis- 4 minutes oak ng; 7 V g, 7 .solved in a suitable photographically inactive water-miscible 5. 5 minutes washing with a solution of g of anhydrous solvent, can be employed. If the same procedure as in Examsodium sulphite per liter; ple 3 is then followed, then on suitable matching the grey 6. 3 minutes soaking; image of the original used, bleached cleanly to white in the ap- 7. 4 minutes development with a solution consisting of 2 g of propriate areas, is again obtained. Calgon, 50 g of anhydrous sodium sulphite, 10 g of 50 hydroquinone, 50 g of anhydrous sodium carbonate", 2 g EXAMPLE 5 of l-phenyl-3-pyrazolidone and 20 ml of a 1% strength tbutyl-aminoborane per liter; I 8. 2 minutes soaking; A hoto ra hic material as described in Example 3 is exposed in th% Ii I ICC spectral ranges as indicated. Thereafter the 6 gi i y j' g "T 3:3 bleachulg h copy is developed asfouows: w 1611 per itre contains m o 0 strength su phur cz l. 7 minutes development in a bath which per litre contains 10 g potasslum odlde 10 ml F a 4 1O 50 g of anhydrous sodium sulphite, 0.2 g of l-phenyl-3- a sohmon 5 Compound H m ethane pyrazolidone, 6 g of hydroquinone, 35 g of anhydrous minutes g Sodium carbonate, 4 g of potassium bromide, 03 g of 11.2 minutes bleaching of the residual silver as described 111 benztriazole and 20 ml of a 4.10 molar solution of com- Example 1 uncle? pound U in dimethyl-formamide 2 minutes i 2 minutes fixing with a solution of 200 g of sodium 13.4m1nutesfixmgas described in Example 1 under 2.),

thiosulphate, 10 g of anhydrous sodium sulphite and 10 l0 F i ml of glacial acetic acid per tel. After drying, an image of the wedge used, cleanly bleached to 2 minutes Soak-mg colourless, with contrary gradation, is obtained. 4. 10 minutes dyestuff bleaching with a solution of 10 g of Instead of the compound Posslble use P potassium iodide in 1 litre ofsulphuric acid pound PP or another of the ouinoxalines described in the ta- 5' 2 minutes soaking ble, in a suitable photographically inactive water-miscible sol- 6. 8 minutes bleaching of the residual silver with a bath vent If Procedure described in example is which contains 150 ml of 37% strength hydrochloric acid, lowed, an Image of the p e g p y bleached to 25 g of copper Sulphate and 30 g of potassium bromide colourless, with contrary gradation, is again obtained.

er liter EXAMPLE 7 7. 2 minutes soaking 8. 3 minutes fixing as under 2.) A solution consisting of 3.3 ml of 6% strength gelatine, 3.3

9.10 minutes soaking. ml of a silver bromide emulsion containing 5.3 g of silver per 100 g of emulsion, 1.0 ml ofa 1% strength Solution of the curing agent described in Example 1, 0.3 ml of a 1% strength solution of the blue-green dyestuff of formula 1.1 described in Example 1, 0.5 ml of a 4 X molar solution of the compound U in dimethylformamide and 1.6 ml of water is cast on a glass plate of size 13 cm X 18 cm. After drying, a step wedge is copied onto the layer thus obtained (50 LUX, 10 sec.) and the copy is processed as described in Example 1.

After drying, a positive image, cleanly bleached to colorless, of the wedge used as the original is obtained.

The compound U can be replaced by the compound EE, dissolved in methanol. If then the procedure described in this example is followed, a positive image, cleanly bleached to colourless, of the original used is again obtained.

Instead of the compound U, it is possible with equally good success to use the quinoxaline 11 from the table, as an alcoholic solution.

EXAMPLE 8 A photographic material as described in Example 3 is exposed in the three spectral ranges as indicated in Example 3. The copy is then treated as follows:

1. 7 minutes development with a bath which per liter contains 20 g of anhydrous sodium sulphite, 10 g of anhydrous sodium carbonate, 4 g of hydroquinone, 1 g of 4- methylaminophenol sulphate, 2 g of potassium bromide and 10 ml of a 4 10' molar solution of the compound U in dimethylformamide;

2. 2 minutes fixing with a solution of 200 g of sodium thiosulphate, 15 g of anhydrous sodium sulphite, 25 g of crystallized sodium acetate and 13 ml of glacial acetic acid per liter;

3. 2 minutes soaking;

4. 10 minutes dyestuff bleaching using a composition which per liter contains 10 g of potassium iodide, 27 ml of 96% strength sulphuric acid and 5 ml of a 4 10' molar solution of the compound U in dimethylforrnamide;

5. 2 minutes soaking;

6. 8 minutes bleaching of the residual silver as described in Example 5 under 6);

7. 2 minutes soaking;

8. 3 minutes fixing as under 2.); and

9. 10 minutes soaking.

After drying, a positive image, cleanly bleached to white, of

the original used is obtained.

EXAMPLE 9 A solution consisting of 3.3 ml of 6% strength gelatine, 2.0 ml of a 1% strength solution of the hardener described in Example l, 3.3 ml of a silver bromide emulsion which contains 5.3 g of silver per 100 g of emulsion, 0.3 ml ofa 1% strength solution of the blue-green dyestuff of formula 1.1) and 1.1 ml of water is cast onto a glass plate of size 13 cm X 18 cm. After drying, a step wedge is copied onto it (50 Lux, 3 seconds) and the copy is treated as follows:

6 minutes dyestuff bleaching with a solution which per liter contains 27 ml of 96% strength sulphuric acid, 10 g of potassi-- um iodide, and in each case 10 ml of a 4 X 10 molar solution of one of the compounds BB, V, R, O, I, E, NN, II or 00 in ethanol or another suitable water-miscible photographically inactive solvent.

After 2 minutes soaking the residual silver is oxidised as described in Example 1 under 6) and the material is soaked and fixed as described above. The copy is thoroughly washed and dried. In each case a blue-green wedge, cleanly bleached to colourless, of which the gradation corresponds to that of the original, is obtained.

EXAMPLE 10 A solution consisting of 3.3 ml of gelatine, 1.0 ml of a 1% strength solution ofthe purple dyestuffofformula 2.0 ml of a 1% strength solution of the hardener described in Example 1, 3.3 ml of a silver bromide emulsion containing 5.3 g of silver per g of emulsion and 0.4 ml of water, is cast onto a glass plate of size 13 cm X 18 cm. After drying, a step wedge is copied thereon (50 Lux, 5 seconds) and the copy is treated as follows:

Developing and fixing as described in Example 1. 6 minutes dyestuff bleaching with a solution which per liter contains 10 g of potassium iodide, 27 ml of 96% strength sulphuric acid and in each case 10 ml of a 4 X 10 molar solution of the compound X, Q, G, B or F in ethanol or another suitable watermiscible photographically inactive solvent. After a brief soaking, the residual silver is oxidised as described above, and the material is soaked and fixed. After thorough rinsing and drying, an image, cleanly bleached to colorless, with a distinctly stepped gradation of the original used is thus obtained in all cases.

EXAMPLE 1 1 A glass plate of size 13 cm X 18 cm is coated with a solution which contains 3.3 ml of 6% strength gelatine, 2.0 ml of a 1% strength solution of the hardener described in Example 1, 3.3 ml of a silver bromide emulsion containing 5.3 g of silver per l0() g of emulsion, 0.5 ml of the yellow dyestuff of formula (11.1) S 0311 CH1 OO N=N l NH 1 I -CO and 0.9 ml of water. After drying, a step wedge is copied thereon (50 Lux, 5 seconds) and the material is treated analogously to Examples 9 and 10, with the colour bleaching bath, instead of containing the compounds mentioned there, containing 10 ml of a 4 X 10' molar solution of one of the substances C, D, P, CC, JJ, LL or G6 in m'ethanolor another suitable waterlmiscible photographically inactive solvent.

Ny A2 as dyestuff bleaching catalyst, in which A and A each is an alkyl radical with at most 5 carbon atoms or a phenyl radical, D is a radical ofthe formula -CN, O-R, COOR or in which R is an alkyl radical with at most five carbon atoms and R, and R, each is a hydrogen atom or an alkyl radical with at most five carbon atoms, and E is a hydrogen or halogen atom, an alkyl or alkoxy group with at most five carbon atoms, a nitro group, an unsubstituted amino group, an alkylammo group with at most four carbon atoms or an acylam no group.

2. Process according to claim 1, which comprises using a quinoxaline of the formula as a dyestuff bleaching catalyst, in which A, and A, each is a methyl or phenyl radical, and D is a radical of the formula OR, COO-R, or

3. Process according to claim 1, which comprises using a quinoxaline of the formula as a dyestuff bleaching catalyst, in which D is an alkoxy group 4. Process according to claim 1, which comprises using a quinoxaline of the formula N\ At as a dyestuff bleaching catalyst, in which D is a methoxy or ethoxy group, E is a chlorine atom, a methyl, methoxy, nitro,

amino, methylamino or acylamino group, in which acyl is the radical of an alkanecarboxylic acid with one to five carbon atoms, benzoic acid, and benzoic acid substituted by halogen, alkyl, nitro, alkoxy, hydroxy or amino and A, and A, each is a methyl or phenyl radical.

5. Process according to claim 3, which comprises using a quinoxaline of the formula as a dyestuff bleaching catalyst, in which D is a methoxy or ethoxy group and E is a methoxy, methylamino or amino group.

6. Process according to claim 2, in which A, is methyl.

7. Process according to claim 6, in which A, is methyl.

8. Process according to claim 5, in which A, and A, is each methyl.

9. Process according to claim 5, in which D is methoxy and A, is methyl.

10. Process according to claim 9, in which A, is methyl.

11. Process according to claim 1, which comprises using a quinoxaline of the formula as a dyestuff bleaching catalyst, in which D is a radical of the formula CN, COOR, or

CON

in which R, and R, each is an alkyl radical with at most five carbon atoms or a hydrogen atom and A, and A, each is an alkyl radical with at most five carbon atoms or a phenyl radical.

12. Process according to claim 11, in which A, and A, each is a methyl or phenyl radical.

13. Process according to claim 12, in which D is a radical of the formula -COOR,, in which R, is an alkyl radical with at most five carbon atoms or a hydrogen atom,and A, is methyl.

14. Process according to claim 13, in which A, and A, is each methyl and R, is hydrogen.

15. Photographic light-sensitive material for the silver dyestufi bleaching process, which contains a quinoxaline of the composition indicated in claim 1 as a dyestuff bleaching catalyst in at least one layer on a support.

16. A photographic processing bath for silver dyestuff bleaching material, which contains at least a quinoxaline of the composition indicated in claim 1 as a dyestuff bleaching catalyst. 

2. Process according to claim 1, which comprises using a quinoxaline of the formula
 3. Process according to claim 1, which comprises using a quinoxaline of the formula
 4. Process according to claim 1, which comprises using a quinoxaline of the formula
 5. Process according to claim 3, which comprises using a quinoxaline of the formula
 6. Process according to claim 2, in which A1 is methyl.
 7. Process according to claim 6, in which A2 is methyl.
 8. Process according to claim 5, in which A1 and A2 is each methyl.
 9. Process according to claim 5, in which D is methoxy and A1 is methyl.
 10. Process according to claim 9, in which A2 is methyl.
 11. Process according to claim 1, which comprises using a quinoxaline of the formula
 12. Process according to claim 11, in which A1 and A2 each is a methyl or phenyl radical.
 13. Process according to claim 12, in which D is a radical of the formula -COOR1, in which R1 is an alkyl radical with at most five carbon atoms or a hydrogen atom, and A1 is methyl.
 14. Process according to claim 13, in which A1 and A2 is each methyl and R1 is hydrogen.
 15. Photographic light-sensitive material for the silver dyestuff bleaching process, which contains a quinoxaline of the composition indicated in claim 1 as a dyestuff bleaching catalyst in at least one layer on a support.
 16. A photographic processing bath for silver dyestuff bleaching material, which contains at least a quinoxaline of the composition indicated in claim 1 as a dyestuff bleaching catalyst. 